While Norse sources claim that Ragnar's sons tortured Ælla to death by the method of the blood eagle, Anglo-Saxon accounts maintain that he died in battle at York on 21 March 867.

Concerning the Norse claim, Roberta Frank reviewed the historical evidence for the ritual in her Viking Atrocity and Skaldic Verse: The Rite of the Blood-Eagle, where she writes: "By the beginning of the ninth century, the various saga motifs—eagle sketch, rib division, lung surgery, and 'saline stimulant'—were combined in inventive sequences designed for maximum horror.

"[1] She concludes that the authors of the sagas misunderstood alliterative kennings that alluded to leaving one's foes face down on the battlefield, their backs torn as carrion by scavenging birds.

[6] The Great Heathen Army, composed mostly of Danish, Norwegian and Frisian Vikings, landed in Northumbria in mid-866 and had captured York by 21 November.

According to the Historia Regum Anglorum, following the invasion of the Danes, the previous "dissension" between Osberht and Ælla "was allayed by divine counsel" and other Northumbrian nobles.

[9] The Anglo-Saxon Chronicle does not name the Viking leaders, but it does state that "Hingwar and Hubba" (probably Ivar and Ubba) later killed King Edmund of East Anglia.

Symeon of Durham lists the leaders of the Viking army as "Halfdene [Halfdann], Inguar [Ingvar], Hubba, Beicsecg, Guthrun, Oscytell [Ketill], Amund, Sidroc and another duke of the same name, Osbern, Frana and Harold.

[12] According to an Anglo-Norman genealogy, Ælla had a daughter named Æthelthryth and through her was the grandfather of Eadwulf of Bamburgh, "King of the Northern English" who died in 913.

[13] According to Ragnarssona þáttr, the army that seized York in 866 was led by Hvitserk, Björn Ironside, Sigurd Snake-in-the-Eye, Ivar the Boneless and Ubba, sons of Ragnar Lodbrok, who avenged his death by subjecting Ælla to the blood eagle.